This invention relates to a process and an apparatus for the one-step manufacture of organic hydrazines in aqueous solutions.
Substituted hydrazines play an important role as intermediates in pharmaceuticals, rocket fuels and starting materials for azo compounds. Prior to the instant invention, there were several methods of preparing hydrazines: one of the commercially significant methods involves starting from chloramine or substituted chloramine and reacting the chloramine with an amine to obtain the desired product. Since chloramine is highly reactive and unstable, in order for a commercial process to be successful, a large quantity of chlorine must be used.
Audrieth, et al. (JACS, 76, 4869, 1954) describes a process for making substituted hydrazine by utilizing aqueous chloramine as a raw material. The preparation of chloramine in an aqueous solution is difficult and must be carried out at low temperatures (about -15.degree. C.) and the amount of alkali in the system must be controlled. Further, only dilute solutions are stable. Sissler, et al. (JACS, 73, 1619, 1951; JACS, 76, 3906, 1954) uses gaseous reactants to prepare substituted hydrazines. This involves the reaction of anhydrous gaseous ammonia with anhydrous chlorine; nitrogen is used as a carrier gas. This method suffers from the by-product of reaction, ammonium chloride, depositing on the reactor walls and plugging up the reactor in a matter of minutes (i.e., 10 to 15 minutes). A later work of Sissler, et al. (ALLEG. PRAKT. CHEM. 21, No. 4, 123-124) describes one way to overcome this problem: the reaction zone is maintained above the sublimation temperature of ammonium chloride. However, this allows only a little more time before the reactor is plugged up. A recent German patent application (Offenlegungschrift No. 24 40 225) describes the addition of a coolant through a split ring to cause ammonium chloride to condense as a fine powder which is carried away from the reaction zone. A large volume of the nitrogen coolant must be used which leads to the dilution of the chloramine; subsequent recovery of excess reactants is made proportionately more difficult. Since some deposition of ammonium chloride takes place, a vibrator is used to loosen the deposits from time to time. The reaction zone is also maintained at a higher temperature to prevent deposits from occurring.
The process of the present invention overcomes the disadvantages of the prior art because the present invention is a one-step process for the manufacture of substituted hydrazines that is carried out at convenient temperatures.